1. Field of the Invention
The present invention relates generally to surface mount device ("SMD") technology and more particularly to a surface mount power supply device having high thermal performance.
2. Description of the Related Art
For many years, the fabrication of an electronic circuit board was accomplished by the "through-hole" method. This method involved interconnecting electronic components on a planar printed circuit board ("PCB") typically comprised of an epoxy/fiberglass laminate substrate clad with an etched sheet of copper to delineate conductive paths. Holes were drilled at the ends of the conductive paths to receive leads of components ("through-hole devices") which were subsequently soldered thereto.
Recently, SMD technology has emerged to allow for more efficient automatic mass production of PCB's with higher component densities. Package components are automatically placed at preselected locations on top of a PCB in such a manner that their leads are aligned with and lie on top of corresponding solder pads. The components are then soldered to the PCB by a soldering process, such as vapor phase soldering, reflow soldering or infrared soldering, to thereby establish a permanent electrical connection between the leads and their corresponding conductive paths.
SMD technology has many advantages over through-hole technology. Most importantly, it avoids the necessity for drilled holes and allows components to be attached to both sides of a PCB. Other important advantages of SMD technology include speed of assembly, greater reliability of components and the availability of large-scale soldering methods. Despite these advantages, the exclusive use of surface mount technology at the PCB assembly level has been stymied by a limited accessibility to certain components that are not yet readily available as SMD's.
Five to thirty watt dc-to-dc converter power supplies are components that are presently not available in surface mount packages. Currently, dc-to-dc converter power supplies are through-hole devices that require different and more costly assembly methods from conventional SMD methods. These devices are commonly used in telecommunication switches, network devices, mainframe computers and minicomputers. Lack of availability of SMD dc-to-dc converters ultimately has prevented manufacturers from realizing the full potential of cost savings from automatic SMD operations. Surface-mountable dc-to-dc converters have been presently available only as custom-built components or standard components in a limited set of inputs and outputs. Switching to surface-mount for dc-to-dc converters would be especially desirable where SMD is already widely used, as in telecommunications, computers, wireless cellular base stations, computer mainframes or work stations. However, weight has been the chief obstacle in constructing these devices to be surface-mountable. An SMD needs to be light enough to be handled by surface mount pick-and-place equipment, but encapsulation and other techniques necessary for effective thermal dissipation have not allowed adequate weight reductions.
It is therefore an object of the present invention to provide a surface-mountable power supply device by making the necessary reductions in component weight for pick-and-place operations while still allowing for effective thermal dissipation.